DENIERS SAY:

The Earth’s climate has natural feedbacks that keep the planet cool. Otherwise, we’d be seeing runaway warming in the Arctic.

SCIENCE SAYS:

The Arctic has been warming twice as fast as the rest of the world.

In recent decades, the Arctic has been warming at twice the global average rate. Recent research finds that melting sea ice plays a central role in this accelerated warming. How does this work? Sea ice acts like a bright white shield that reflects a portion of the sun’s rays back into space. Deep blue ocean water, however, is less effective in reflecting sunlight. It absorbs a lot more of the sun’s energy, which results in warming. Warming, of course, results in less ice, which in turn results in more warming. It’s a troubling feedback loop.

Additional info from the National Snow and Ice Data Center

The sun's rays strike the polar regions at a more grazing angle than over equatorial regions, where the rays strike at a more direct angle. The sun's angle is the primary reason why the polar regions are cold and the equatorial regions are warm.

Sea ice is white, so nearly all of the sunlight that hits the sea ice surface is reflected back into space; thus, it has a high albedo. High albedo helps keep the polar regions cold, because the sunlight reflected back into space does not warm the surface. When the climate changes enough to warm the Arctic and to melt sea ice, the polar regions have less of a reflective surface. More heat is absorbed, which causes more melting, which amplifies the warming. This cycle is technically known as a “positive feedback loop” that ultimately alters the circulation of the atmosphere — although the outcome is far from positive.